R.I. Gen. Laws § 21-28-5.08: Burden of proof.

(a) It shall not be necessary for the state to negate any exemption or exception set forth in this chapter in any complaint, information, indictment, or other pleading or in any trial, hearing, or other proceeding under this chapter, and the burden of pleading and proof of any exemption or exception shall be upon the person claiming its benefit.

(b) In the absence of proof that a person is the duly authorized holder of an appropriate registration or an official written order issued under federal law, he or she shall be presumed not to be the holder of the registration form, and the burden of proof shall be upon him or her to rebut the presumption.